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Unformatted text preview: 287 IDENTIFICATION BY DENSITIES OBJECTIVES FOR THE EXPERIMENT The student will be able to do the following: 1. Write or identify the definitions of density, bulk density, and absolute density. 2. Measure mass using an electronic balance. 3. Measure volume using a graduated cylinder. 4. Calculate masses using the procedure called weighing by differences. 5. Calculate volume using the procedure called volume by displacement. 6. Given all but one of the following, calculate the one not given: density, mass, and volume. 7. Identify an unknown substance from comparison of the density of the substance with a table of densities of known substances. 8. Report all data from measurements or calculations with the correct units, exponential notation and sig- nificant figures. BACKGROUND ON DENSITY Density is mass per unit volume. mass volume Density = Densities can be used for many purposes. A chemist might use density measurements to help identify an unknown substance by comparing its density with a list of known densities. An engineer might use the density to calculate the mass or volume of a substance that is being used in construction. She might calculate the mass of concrete in a bridge pier of known volume. There are two types of density. Bulk density is mass divided by the bulk volume. Bulk volume includes the volume of the particles of a substance and the air in between the particles. The bulk volume of sand is the volume of the sand particles and air between the particles. mass bulk volume Density = The mass of dry sand divided by its observed volume yields its bulk density....
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